PC and PES exhibit excellent characteristics in transparency, heat resistance, mechanical strength, and the like, but are not always satisfactory in terms of moisture impermeability and oxygen barrier property for practical use.
In order to overcome these disadvantages while retaining the advantages inherent to these resinous polymers, it has been proposed to laminate a PC or PES layer with a resinous polymer having counterbalancing characteristics, such as polyolefins excellent in moisture impermeability or a saponified ethylene-vinyl acetate copolymer (EVA) excellent in oxygen barrier property. In particular, these attempts have been studied intensively in the fields of co-extrusion molding and co-injection molding that are suited for efficient production of laminated structures, and, in addition, orientation subsequent to the molding.
For example, polyolefins graft-modified with unsaturated carboxylic acids or the derivatives thereof have been proved adhesive to PC or PES as disclosed in Japanese Laid-Open Patent Application Nos. 125588/77 and 32078/77. However, as shown in working examples of the respective publication, the initial adhesion strength of these modified polyolefins is as low as from 150 to 200 g/cm for PC and from 200 to 270 g/cm for PES. Moreover, these laminated structure undergo drastic reduction in adhesion strength under a high temperature and high humidity condition as in retort processing as demonstrated in comparative examples hereinafter given.
That is, in lamination of PC or PES with a polyolefin or a saponified EVA by co-extrusion or co-injection molding, there has been found no high performance adhesive which achieves strong adhesion between these resinous polymers and is also excellent in heat endurance, and therefore laminated structures applicable to a broad field have not been provided.